CI Automation/windows10 aarch64

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Since mid-January 2019 the CI-A team has been working to enable existing test harnesses, continuous integration tests and other tools to run on Windows 10 ARM64.

General Information


  • Make: Lenovo
  • Model: C630 YOGA
  • Processor: Qualcomm Snapdragon 850 3.0GHz
  • Cores: 8
  • Memory: 8GB
  • Disk: 128GB SSD


Currently an array of 28 machines are hosted at Bitbar in the United States.


Test environment

There are two methods by which developers are able to run tests with a windows10-aarch64 hardware locally.


  1. download Mozilla-Build 2.2.0
  2. install Mozilla-Build 2.2.0
  3. download the test runner script from bug 1520867


This method installs an older version of Mozilla-Build on the system to execute tests.

  1. place the script in the mozilla-build directory
  2. copy the task ID from treeherder for the windows10-aarch64 Build (artifact is supported)
  3. invoke start-shell.bat, which will launch a bash-like command line
  4. from mozilla-build directory, run the test runner script as follows:
bash task_id test_type <chunk_to_run> <total_chunks>


bash Q-CE8DFvSAWmc08vw6bd6A xpcshell 1 8


This method is taken from this guide.

  1. invoke start-shell.bat, which will launch a bash-like command line
  2. clone the repository with hg clone
  3. run ./mach bootstrap and pick artifact build
  4. download python3 as embeddable zip, then extract to mozilla-build/ directory
  5. comment out this line
  6. download 32bit NodeJS zip and extract to .mozbuild/node
  7. inside mozilla-build, remove watchman directory
  8. retry ./mach bootstrap

After the artifact build succeeds, it is possible to run most suites of tests as normal:

./mach mochitest

CI environment

Tests that are run in Taskcluster environment against windows10-aarch64 execute using Taskcluster Generic-Worker. These are installed as a service on via OpenCloudConfig.


This is the method used in production.

Steps originally taken from 1520432.

$gitBranchOrRef = 'master'
Invoke-Expression (New-Object Net.WebClient).DownloadString(('{0}/userdata/rundsc.ps1?{1}' -f $gitBranchOrRef, [Guid]::NewGuid()))

Manually install Taskcluster Generic-Worker [Not recommended]

Follow these step to install Taskcluster Generic-Worker on the hardware, and have it launch as a service.

Instruction originally from 1522997.


  • disable Windows S mode
  • disable User Account Control
  • disable Windows Firewall
  • download NSSM to C:\nssm-2.24\
  • create "Remote Desktop Users" group:
net localgroup "Remote Desktop Users" /add
  • log in to Taskcluster
  • request scope `assume:project:taskcluster:generic-worker-tester`


  1. download the current 386 release of `generic-worker-windows-386.exe` from taskcluster generic-worker.
  2. download the latest 386 version of livelog.exe and taskcluster-proxy.exe.
  3. create new directory C:\generic-worker.
  4. move the three executable files under C:\generic-worker.
  5. rename generic-worker-windows-386.exe to generic-worker.exe.
  6. generate two signing keys:
generic-worker new-openpgp-keypair --file <unique_file_name>
generic-worker new-ed25519-keypair --file <unique_file_name>
  1. create generic-worker.config and include the following:
"accessToken":                "<access token tied to taskcluster>",
"clientId":                   "<client ID tied to taskcluster>",
"ed25519SigningKeyLocation":  "<file location you wrote ed25519 private key in step 6>",
"livelogSecret":              "<any text>",
"provisionerId":              "test-provisioner",
"publicIP":                   "<ideally an IP address of one of your network interfaces>",
"rootURL":                    "",
"workerGroup":                "test-worker-group",
"workerId":                   "test-worker-id",
"workerType":                 "<a unique string that only you will use for your test worker(s)>"
  1. launch cmd.exe with Administrator rights.
  2. cd c:\generic-worker
  3. generic-worker.exe install service --config generic-worker.config --nssm c:\nssm-2.24\win32\nssm.exe
  4. reboot once installed.
  5. launch cmd.exe with Administrator rights.
  6. sc query "Generic Worker"

Currently Running

Currently supported list of tests include:

  • awsy
  • mochitest (all flavors)
  • reftests
  • xpcshell
  • raptor
  • marionette

Supported, requires non-artifact build:

  • cppunittest

There is remaining work needed to get these test suites running:

  • talos
  • web-platform-tests (all flavors)

For an up-to-date list of tests, please refer to this file.

Run tests on Try

This is probably what you came to the document for. How to run tests against the windows10-aarch64 hardware currently available.

Note, the number of hardware is limited so please exercise caution when scheduling tests - a careless try can easily backlog other developers looking to test their changes.


Follow these steps to be able to enable windows10-aarch64 tests for the try server. These steps are required as of 2019-02-25; it will become obsolete when windows10-aarch64 tests are released to the general public.


  • try access (commit access level 1)
  • up-to-date mozilla-central codebase


  1. open the file at taskcluster/ci/test/test-platforms.yml
  2. search for 'windows10-aarch64/opt'
  3. uncomment all or some of the items under 'test-sets'
  4. make changes to the local codebase that needs testing
  5. ./mach try fuzzy
  6. select tests that need to be run (e.g. 'windows10-aarch64 xpcshell')
  7. enter

Tests will appear in Treeherder under the heading windows10-aarch64 opt.

Greening tests

Since Windows on ARM64 is a new platform/architecture combination, failures unique to this combination is to be expected. It will be necessary to fix, correct or update the tests in order to obtain a green run.

Example 1

As part of 1525743, the timeout for mochitest-browser-chrome was extended to 4x the default value if the platform combination of Windows and ARM64 is detected.

See change:

This change greened the test that was previously failing due to a timeout.

Example 2

Some tests provide a manifest file in the form of <test_category>.ini, such as mochitest.ini.

For bug 1525665 it was determined to disable a certain a11y test while windows10-aarch64 a11y support was being investigated.

See change:

This change meant the failing test is now disabled for windows10-aarch64, and the test would have been green had it not been for another failure elsewhere.

Example 3

Another example of manipulating the manifest of a category of tests, this time with web-platform-tests.

For Bug 1533912 the manifest was modified to disable the test if it was running on aarch64 hardware.

See change:

Note that web-platform-tests use a slightly different format in order.

Example 4

Certain test cases in reftest/crashtest/jsreftest had unexpected outcomes on windows10-aarch64.

For Bug 1536365 and 1536363 the requirement was to adjust the pixel difference values such that tests will pass.

See change:


These are the top-level tracking bugs; the recommended view is tree (login required).

Full Query
ID Summary Priority Status
1520867 Investigate running tests on Windows / arm64 P1 RESOLVED
1523722 Run gtest using generic-worker on Windows/aarch64 P3 ASSIGNED
1524114 Run xpcshell-test using generic-worker on Windows/aarch64 P3 ASSIGNED
1524400 Run mochitest using generic-worker on windows/aarch64 P3 ASSIGNED
1524410 Run reftest suites using generic-worker on windows/aarch64 P3 ASSIGNED
1525118 [meta] Run taskcluster task from mach try on Bitbar -- RESOLVED
1525434 Run web-platform-test suite using generic-worker on windows/aarch64 P3 NEW
1526015 Run cppunit, jittest, marionette using generic-worker on Windows/aarch64 P3 NEW
1527177 Intermittent [taskcluster:error] [mounts] reading file in zip archive: file already exists: Z:\task_1549919043\mozharness\LICENSE P5 RESOLVED
1527469 Enable windows10-aarch64 build and tests on try server -- RESOLVED
1530737 unable to run talos/raptor on win/aarch64 builds in CI -- RESOLVED
1531876 run talos/raptor tests on windows10 aarch64 laptops P1 RESOLVED
1531878 [taskcluster:error] [mounts] reading file in zip archive: file already exists: C:\tasks\task_1551392763\mozharness\LICENSE P1 NEW
1531927 windows/aarch64 - skipped/disabled media tests P5 REOPENED
1533114 windows/aarch64 - skipped/disabled a11y tests P5 NEW
1533880 windows/aarch64 - skipped/disabled web-platform-tests P5 NEW
1534823 windows/aarch64 - skipped/disabled mochitest tests P5 NEW
1535467 windows/aarch64 - test screenshots sometimes show "Windows Defender Firewall has blocked some features of this app" P3 ASSIGNED
1536208 windows/aarch64 - skipped/disabled xpcshell tests P5 NEW
1536283 [meta] windows/aarch64 - skipped/disabled marionette tests P5 NEW
1536354 windows/aarch64 - skipped/disabled reftests P5 NEW
1538785 windows/aarch64 - plugin tests failing on windows10-aarch64 -- RESOLVED
1539693 windows/aarch64 - re-enable/adjust web-platform-tests results based on new timeout multiplier -- RESOLVED
1540213 windows/aarch64 - enable tests for windows10-aarch64 on taskgraph -- RESOLVED
1543521 windows/aarch64 - lower windows10-aarch64 to tier 2 on try -- RESOLVED
1545810 windows/aarch64 - web platform test chunk investigation -- NEW
1546532 windows/aarch64 - enable mochitest-a11y -- ASSIGNED

27 Total; 17 Open (62.96%); 10 Resolved (37.04%); 0 Verified (0%);